I have to admit...that little 4 word campaign bumper sticker (MAGA) has been an effective tool for DJT. He owes his entire presidency to whoever came up with it and/or convinced him to use it.
It's simplistic and nebulous enough to not mean anything, and at the same time, it means everything.
To you, it harkens back to all the aspects you so eloquently listed above. Who could argue with any of that? Everything you listed obviously represents our country's most laudable events. If it truly rings that bell for you, who could blame you?
At the same time, it does, ever so subtly, imply a less positive meaning...and the further you move down the intolerance path, the more powerful it becomes. As bawlmer said, we will never find greatness by looking back. Greatness is a never ending journey...kind of like golfers who talk about the impossibility of a perfect golf swing. Greatness is achieved by striving for greatness, not convincing ourselves we have already reached it.
So, huzzah to the political staffer who was able to convince Trump to utilize that phrase. It resonated all across the GOP spectrum...from middle of the road conservatives to the most extreme alt-right, Qanon dumb shits...it was fluffy red meat cotton candy that pulled everyone under those tent flaps of the Right Wing.